Exhibit 2.1 AMENDMENT NO. 1 TO STOCK PURCHASE AGREEMENT THIS AMENDMENT NO. 1, dated as of March 23, 2004, to the STOCK PURCHASE AGREEMENT, dated as of February 2, 2004, is entered into by and among Ameren Corporation, a Missouri corporation...Stock Purchase Agreement • March 24th, 2004 • Cilcorp Inc • Electric & other services combined
andCilcorp Inc • November 5th, 1999 • Electric & other services combined • New York
225,000,000 8.700% Senior Notes due 2009 $250,000,000 9.375% Senior Bonds due 2029 REGISTRATION RIGHTS AGREEMENT Dated as of October 18, 1999Registration Rights Agreement • November 5th, 1999 • Cilcorp Inc • Electric & other services combined • New York
RIGHTS AGREEMENTRights Agreement • October 29th, 1996 • Cilcorp Inc • Electric & other services combined • Illinois
EXCHANGE AGENT AGREEMENTExchange Agent Agreement • November 5th, 1999 • Cilcorp Inc • Electric & other services combined • New York
CILCORP INC.,Cilcorp Inc • November 5th, 1999 • Electric & other services combined • New York
PAYER'S NAME: [PAYING AGENT] -------------------------------------------------- --------------------------------------------------------------Cilcorp Inc • November 5th, 1999 • Electric & other services combined
